1. Field of the Invention
The present invention relates to the use of high molecular weight polyvinylamines as flocculants and, more especially, relates to the use of the higher molecular weight polyvinylamine hydrochlorides for the flocculation of suspended solids in water purification or waste water clarification systems.
2. Description of the Prior Art
Stable colloids or suspensions arise in many civil and industrial processes and their treatment often poses a problem. Notable examples are the clarification of turbid water for human consumption and the control of pollution in municipal and industrial waste water. The treatment of such systems commonly utilizes flocculation, a process in which small particles are agglomerated and hence settle more rapidly and are more readily filtered, This procedure is critically used in such diverse fields as paper making and mining, although the dominant market for such flocculants is potable water purification and sewage pollution control.
Heretofore, alum and ferric chloride have been the principal commercial flocculants. More recently, attention has focused on the use of synthetic polymers in flocculation systems. The rapidly expanding role of synthetic polymers as flocculant aids is attributable to their ability to greatly reduce the requisite quantities of inorganic flocculants and to impart superior flocculation behavior such as faster settling rates and improved filterability. Other factors that militate against the use of inorganic flocculants alone in waste-water treatment are their corrosiveness and their conversion to non-combustible oxides during the sludge burning process.
Thus far a number of polymers have been commercialized for water treatment. These include polyacrylic acid, polyarylamide and its partial hydrolysis product, cationic starch, polyethylenimine and polystyrene sulfonates. See, e.g., J. K. Dixon, "Flocculation", In Encyclopedia of Polymer Science and Technology, V. 1, N. M. Bikales, Ed., Wiley-Intersciences, N.Y. 1967.
Although the use of polyvinylamine and copolymers of vinylamine and vinyl alcohol as flocculants has been suggested (see, e.g., Terres Eaux, 1968, 21 (55) 27-8 and U.S. Pat. No. 3,715,336) there is substantial authority for the proposition that polyvinylamine actually exhibits deflocculation characteristics. (See, e.g., Chemical Abstracts, 49, 12801h (1955)). It is, therefore, evident that thus far the prior art has failed to appreciate the significance of polyvinylamine as a flocculating agent, and, in truth, has discouraged the use of polyvinylamine in this regard by ambiguous teachings.